Adding and subtracting a
monomial requires having the same variables. No matter how big or small their
coefficient is, if their variables do not match, they cannot be added or subtracted.
The crucial part in adding or subtracting monomials is their sign. If the signs
are the same, retain the sign. If the signs are different, subtract and keep
the sign of the larger number.
3x2y + 3xy (cannot be added)
3x2y + (–12x2y) = -9x2y
3x2y + 2x2y2 (cannot be added)
3x2y + 7xy2 (cannot be added)
3x2y + (–10x2) (cannot be added)
3x2y + 4x2y = 7x2y
3x2y + 3x3 (cannot be added)
